Oh that’s what you meant. In that case I see what you mean, but I’m not convinced. First, doing such a thing would destroy their own seat of power, as most revolts tend to start in the capital or reach it pretty quickly. Second, it would immediately spark a coup, civil war or intensify the revolution, for the same reason Assad’s gassing didn’t stop the Syrian revolution. The level of destruction a nuke can cause can be more or less replicated using conventional means, using a nuke means dealing with nuclear fallout which even the most maniacal governments wouldn’t put themselves through and using drastic violence tends to push people towards militancy rather than compliance. Third, it’d destroy their international legitimacy, give Western countries an excuse for drastic intervention and discourage their allies from helping them defend against such an intervention. Iran’s government is certainly evil, but they’re rationally evil, and nuking one’s own people is very much not rational.